Refrigerator

ABSTRACT

A heat insulating box of a refrigerator includes a non-flammable heat-insulator particularly a vacuum heat-insulator made of a board-shape molded inorganic fiber. Therewith non-flammability of the heat insulator is ensured and a refrigerator box prevented from catching an outside caused fire is achieved, thus a refrigerator which is safe even when a flammable refrigerant is used and which is high in energy-saving is provided.

TECHNICAL FIELD

This invention relates to a refrigerator, which safety is enhanced bysecuring non-flammability of a heat-insulator and which energy savingproperty is enhanced by improving non-flammability of theheat-insulator.

BACKGROUND ART

A conventional refrigerator cools or freezes foodstuff by having anevaporator constituting a refrigeration cycle in a space formed by arefrigerator box, and disposing a heat insulating material in the boxfor insulating a cool air produced by the evaporator from an outsideair.

Recently, a vacuum heat-insulator having a high heat-insulatingcharacteristic is attracting a public attention from energy-saving andspace-saving standpoints. Examples of such vacuum heat insulators aresuch as one which core material is made of hard-urethane-foam havingcontinuous foam, covered by a gas-barring laminated film and then insideis vacuumed, and another one which inorganic material powder is filledin an inside bag, and the bag is put in an outside bag and then theoutside bag is decompressed. Heat-insulating characteristic of thosevacuum insulators is 2.5 times higher than that of foam resin insulatorcomposed of hard or soft urethane-foam material.

The foam resin material used in the conventional refrigerator is not soeffective as to prevent the heat-insulating material from burning from afire, if a fire is broken out near the refrigerator and theheat-insulating box catches the fire. Using a vacuum heat-insulatorhaving a high heat-insulating characteristic is an effective way for arefrigerator to enhance energy-saving characteristic and increase astorage capacity of the refrigerator. However, the vacuum heat-insulatorusing the foam resin as a core material does not much contribute toincreasing non-flammability of the refrigerator. If a vacuumheat-insulator employs an inorganic-material powder, non-flammability ofthe insulator increases, however, because the material is hard to bemolded into a heat-insulator, it is difficult to be used for aheat-insulator of a refrigerator. Moreover, as flammable hydrocarbon(HC) refrigerant is started to be used for preventing global warming, arefrigerator avoided from catching a fire is becoming more important.Yet the conventional heat-insulating material does not comply with suchrequirement.

The present invention is aimed to solve above conventional tasks and toprovide a refrigerator which is safe for using a flammable refrigerantand high in energy saving property. The refrigerator uses anon-flammable vacuum heat-insulator made of a board-shape moldedinorganic fiber in the refrigerator box, thus preventing therefrigerator box from catching an outside fire.

SUMMARY OF THE INVENTION

In order to solve above tasks, a heat-insulator of the refrigerator inthe invention includes a vacuum heat-insulator which is composed of aboard-shape molded inorganic fiber covered by a gas-barring film andevacuating inside, a foam resin heat-insulator in its heat insulatingbox. Having the non-flammable vacuum heat-insulator composed of theboard-shape molded inorganic fiber, non-flammability of theheat-insulating box is enhanced higher than a heat-insulating box havingonly of the foam resin. Non-flammability of the heat insulating boxagainst an outside fire is thus improved, a refrigerator having a highersafety than a conventional refrigerator is provided.

Because the vacuum heat-insulator is disposed inside the heat insulatingbox reducing usage of the foam-resin in the box, enhancing thenon-flammability of the heat-insulating box, a wall of the heatinsulating box can be thinned so that a total amount of the foam-resinused in the box can still be reduced. Because the usage amount of thefoam resin is reduced, generation of organic gas is avoided even whenthe insulating material catches a fire, and a much safer refrigerator isrealized.

Because the molded board-shape inorganic fiber is used with theheat-insulator, the refrigerating box is made flat in outside surface,light in weight and high in productivity.

The refrigerator in this invention includes heat-insulating materials ina space between an inner box and an outer box, and the vacuumheat-insulator made of the board-shape molded inorganic fiber is placedon the outer box. The vacuum heat insulator is placed on the outer sidebox of the refrigerator and the vacuum heat-insulator is non-flammable,even when the refrigerator catches an outside fire, foam resin hardlycatches the fire because the vacuum heat-insulator is non-flammable,because the vacuum heat-insulator is non-flammable, improvingnon-flammability of the refrigerator box.

A door also includes the non-flammable vacuum heat-insulator composed ofthe board-shape molded inorganic fiber, so that non-flammability of thedoor heat-insulator is enhanced against a fire outside the refrigerator.

The refrigerator also includes a partition box dividing the refrigeratorinto independent compartments, and the partition box of the refrigeratoralso includes the vacuum heat-insulator composed made of the board-shapemolded inorganic fiber. Because of this structure, even when one of theindependent compartments a freezing compartment or a refrigeratingcompartment catches an outside fire, the non-flammable partition boxhardly burns preventing the other compartment catches the fire, thus therefrigerator is given a further enhanced safety.

The refrigerator according to the present invention has the board-shapemolded inorganic fiber in the space between the outer box and the innerbox constituting the refrigerator box and the space is evacuated. Thevacuum space need not include the foaming resin. Because of this reason,non-flammability of the box can be greatly increased. Even when therefrigerator catches a fire, generation of organic-gas from the foamresin is eliminated beforehand, so the safety of the box is greatlyenhanced. Besides, the heat insulating box by itself can be a vacuumheat-insulating, so heat insulating characteristic of the refrigeratoris greatly increased.

The board-shape molded inorganic fiber includes at least silica.Employing an inorganic fiber including silica, a vacuum heat-insulatorhaving a superior heat-resistance and of low cost can be provided.

The board-shape molded inorganic fiber includes at least alumina. Byemploying an inorganic fiber including alumina or by increasing thepercentage of alumina, non-flammability of the board-shape moldedinorganic fiber can be further improved, providing the vacuumheat-insulator with much enhanced non-flammability.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross-sectional view of a refrigerator in accordance with afirst exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of a vacuum heat-insulator inaccordance with the first exemplary embodiment of the present invention.

FIG. 3 is a cross-sectional view of a refrigerator in accordance with asecond exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention are described hereinafterwith reference to the drawings.

First Exemplary Embodiment

FIG. 1 is a cross-sectional view of a refrigerator in accordance with afirst exemplary embodiment of the present invention. Refrigerator mainbody 1 is composed of heat insulating box 2, partition box 3, door 4,and a refrigeration cycle composed of compressor 5, condenser 6,capillary tube 7 and evaporator 8. Heat insulating box 2 and door 4 arecomposed of outer box 9 made of press-molded iron plate or the like andinner box 10 is made of molded ABS resin or the like.

A refrigerator space is formed by heat insulating box 2 and door 4. Thespace is divided into an upper space and a lower space by partition box3, the upper space being refrigerating compartment 11 and lower spacebeing freezing compartment 12.

Compressor 5, condenser 6, capillary tube 7, and evaporator 8 are linkedtogether constituting the refrigeration cycle. In the refrigerationcycle of the exemplary embodiment of the present invention, isobutene isenclosed as a HC refrigerant. Evaporator 8 sends a cool air intorefrigerating compartment 11 through damper 13 placed in freezingcompartment 12. Evaporator 8 can be installed in two places, both inrefrigerating compartment 11 and freezing compartment 12 connected inseries or in parallel forming the refrigeration cycle.

In space 14 of the heat-insulating box and in space 15 in door 4, vacuumheat-insulator 16 and foam resin heat-insulator 17 are placed. Foamresin heat-insulator 17 in this exemplary embodiment is hard urethanefoam foamed by a foaming agent cyclopentane. In partition box 3, vacuumheat-insulator 16 is placed.

In vacuum heat-insulator 16 in the exemplary embodiment, a board-shapemolded inorganic fiber is used as a core material. The core material iscovered by a gas-barring film and inside is vacuumed, providing vacuumheat-insulator 16.

Constituent element of the board-shape molded inorganic fiber is notspecifically prescribed, but an inorganic fiber such as of aluminafiber, ceramic fiber, silica fiber, zirconium fiber, glass wool, lockwool, calcium-sulfate fiber, silicon-carbonate fiber, potassium-titanatefiber and magnesium-sulfate fiber can be used. Single material is not arequisition for use. Diameter of the inorganic fiber is preferably 10 μmor less from a standpoint of heat-insulation, more preferably 5 μm orless, most preferably 3 μm or less.

Only the fiber material is employed, but an inorganic binder or anorganic binder can be added for forming a collection of the fiber. Asthe inorganic binder, material such as colloidal silica, water glass,low-melting point glass, alumina sol, silicon resin and other knowninorganic binder can be used without restriction.

As the organic binder, thermosetting resin such as phenol resin, epoxyresin, urea resin, acrylic resin including methyl acrylate, ethylacrylate, butyl acrylate, cyano acrylate, methyl methacrylate, ethylmethacrylate, butyl methacrylate, cyano methacrylate, polyethyleneterephthalate, polybutylene terephthalate, polyethrene, polyesterincluding polyethylene naphthalate, polypropylene, polyethylene,polystyrene, poly vinyl acetate, polyvinyl alcohol, polyacrylonitride,and thermosetting resin such as polyamide resin can be used withoutrestriction. Other public known material can also be used with norestriction.

An adding amount of the organic binder is preferred to be 10% or lessfrom standpoints of keeping non-flammability of the inorganic moldedfiber, preventing gas generation over time and maintaining a desireddensity of the material, or more preferably 5% at most. Two or more ofbinders can be mixed together. Generally used plasticizer, thermalstabilizer, optical stabilizer and filling material can also be mixed.Those materials can be mixed for use or can be diluted with water orwith other known organic solvent.

The inorganic fiber material is coated with such binder or with dilutedsolution of the binder, or the inorganic fiber can be impregnated withthe binding material or the diluted solution of it, so that the binderis attached to the inorganic fiber material. If the binder is a dilutedsolution, the binder is dried out first, and the processed inorganicfiber material is compressed or heat-compressed so as to be made into amolded board-shape inorganic fiber. It is also possible to get suchprocessed fiber by diffusing the inorganic fiber material in the dilutedsolution of the binder and then filtering the fiber material out.

The density of the board-shape molded inorganic fiber thus produced is,although not specifically designated, preferred to be at least 80 kg/m³so as it can be formed into a molded unit, and at most 400 kg/m³ so asthe heat-insulating property may be retained; most preferably 150 kg/m³at least and 300 kg/m³ at most.

FIG. 2 is a cress-sectional view of vacuum heat-insulator 16, whichshows that board-shape molded inorganic fiber 18 is placed insidegas-barring film 19 a cover material, and inside is decompressed toapproximately down to 30 Pa.

The gas-barring film covers the core material so that inside can bedecompressed. Constitutional material of the film is not specificallyprescribed, but examples are as follows. Material of an outermost layeris polyethylene terephthalate resin, an intermediate layer is aluminum(hereinafter called AL) foil, and an innermost layer is a plasticlaminate film made of high-density polyethylene resin forming a bag. Inanother example, an outermost layer is polyethylene terephtalate resin,an intermediate layer is ethylene-vinyl alcohol copolymer resinevaporated with AL layer (Kuraray's brand name Eval), and an innermostlayer is a plastic laminate film of high-density polyethylene resinforming a bag.

As features of the cover material, the outermost layer endure an outsideshock, the intermediate layer securely bars gas, and innermost layerseals the bag with heat. As long as such requirements are satisfied, anyknown material is allowed to be used. In order to enhance the feature,such as nylon resin can be deposited over the outermost layerstrengthening resistance to pricking, or two layers of ethylene vinylalcohol copolymer resin having an intermediate layer of AL evaporationfilm can be laid over instead.

For the heat-sealed innermost layer, high-density polyethylene resin ispreferred for its sealing characteristic and chemical resistance, butothers such as polypropylene resin or polyacrylonitride resin can beused without problem.

Shape of the outside cover is not restricted, but any shape is allowedincluding four-way sealing bag, gazette type bag, pillow type bag andL-shape.

It is possible to apply heat-treatment to the core material for removingresidual water and residual gas before the material is placed inside thecover material. The temperature of heat-treatment shall be preferably100° C. or more where at least dehydration occurs.

In order to enhance reliability of vacuum heat-insulator 16, a gettermaterial such as a gas-adsorbent and a moisture-adsorbent can be added.

Adsorption mechanism of the getter can be of a physical or a chemical,or the getter can be of an occlusion type or an adsorption type, but inany case material which works as a non-evaporation getter is preferred.

As a physical adsorbent, such as synthetic zeolite, active carbon,active alumina, silica gel, dawsonite, hydrotalcite are morespecifically listed.

As a chemical adsorbent, oxide material of alkali-metal or ofalkaline-earth metal, hydroxide material of alkali-metal or ofalkaline-oxide metal can be listed, especially lithium oxide, lithiumhydroxide, calcium oxide, calcium hydroxide, magnesium oxide, magnesiumhydroxide, barium oxide and barium hydroxide can be named.

Calcium sulfate, magnesium sulfate, sodium sulfate, sodium carbonate,potassium carbonate, calcium chloride, lithium carbonate, unsaturatedfatty acid, and iron compound also effectively work as a getter. Bariummagnesium, calcium, strontium, titan, zirconium and vanadium can be usedmore effectively as a single material or as an alloy. The getters can bemixed in various ways for absorbing and eliminating nitrogen, oxygen,moisture and carbon dioxide.

Thermal conductivity which represents heat-insulating characteristic ofvacuum heat-insulator 16 made of the board-shape molded inorganic fiberis 0.0043 W/mK at a decompressed condition of 30 Pa. On the other hand,a thermal conductivity made of the vacuum heat-insulator employingcontinuous foam urethane or silica powder as a core material is 0.0065to 0.0075 W/mK at 30 Pa. As shown, heat-insulating characteristic ofvacuum heat-insulator 16 in accordance with the exemplary embodiment isapproximately 1.5 times higher than the conventional vacuumheat-insulator. Because of its high heat-insulating characteristic, eventhin heat-insulator 16 is endowed with a sufficient heat-insulatingcharacteristic, increasing a storage capacity of refrigerator main body1.

Because vacuum heat-insulator 16 uses the core material made of theboard-shape molded inorganic fiber, vacuum heat-insulator 16 is madethin and highly flat, consequently the heat-insulating wall ofinsulating box 2 is made thin and very flat.

Because of its excellent cutting and bending and because it is easy toform a depression, protrusion and a through-hole, vacuum heat-insulator16 can well fit into the shape of refrigerator main body 1. Forinstance, a sheet of vacuum heat-insulator 16 can be placed onto threesides of heat-insulating box 2 of refrigerator main body 1 by bendingalong the side lines. Being formed into such shape, the vacuum heatinsulator can cover edge portions of the refrigerator main body 1,providing heat-insulating box 2 having an excellent non-flammability andheat-insulating characteristic to be used for the refrigerator.

Where a thinner part is required in the wall of heat-insulating box 2,one sheet of the board can be applied there while two sheets be appliedto the other part, thus simply achieving a required shape. Because thecore material of vacuum heat-insulator 16 is in the board shape, variousshape of requirement can be satisfied, while the board can be stackedinto a required thickness.

When a pipe or a conductive wire are placed over vacuum heat-insulator16 as needed by a structure of refrigerator main body 1, depression canbe formed in a shape of the pipe or the wire on the board-shapeinorganic molded fiber when vacuum heat-insulator 16 is fabricated orafter vacuum heat-insulator 16 is fabricated, for the pipe or the wirethere to be placed there. It is also possible to press the vacuumheat-insulator directly onto the pipe or the wire laid inside theinsulating box, by putting the vacuum heat-insulator 16 directly insidethe box. As described, because collected fiber material is used, moldingis easy and formation of depression is easy.

Since the vacuum heat-insulator employs the inorganic fiber,deterioration of vacuum heat-insulator 16 due to temperature rise, whichis caused when foam resin 17 is foam-filled into space 14 between outerbox 9 and inner box 10 of refrigerator main body 1, is controlled withina smaller rang than the vacuum heat-insulator employing the organic corematerial. When fabricating the vacuum heat-insulator employing theinorganic powder, the inorganic powder must be first put into an innerbag then it is put into the outer cover. This is for preventing theinorganic powder from scattering when the cover is evacuated. Thus, forthe powder to be put in an inner bag fabricating the inner bag, theshape of the bag must be properly formed. When the board-shape corematerial is used, however, the vacuum heat-insulator can be formed in arequired shape by just cutting the board-shape core material into therequired shape. When the powder material is used in the vacuumheat-insulator, the inner bag is sometimes broken or the powder isoff-centered when the bag is formed into a required shape, thusrestricting the formation process and deteriorating work efficiency.Because vacuum heat-insulator 16 is a board-shape molded inorganicfiber, work efficiency is much higher in producing vacuum heat-insulator16 than when inorganic powder is used. Because the filling process ofpowder into bag is unnecessary and scattering of powder is prevented,work environment is greatly improved. Moreover, because the corematerial does not scatter even when vacuum heat-insulator 16 is burst,the refrigerator is scrapped without contaminating work environment,namely the refrigerator using the vacuum heat-insulator 16 can bescrapped without difficulty. Still more, because the core material iscomposed of the fiber not of the powder, contact points of the fiber areincreased and the fiber is easily solidified with the binder, mucheasily producing the core material.

In the exemplary embodiment, vacuum heat-insulator 16 and foam resinheat-insulator 17 are included in heat insulating box 2. Foam resinheat-insulator 17 is made of hard urethane foam, phenol foam, or styrenefoam, although the material is not specifically prescribed. Foamingagent that helps foaming of the hard urethane foam is not specificallyprescribed either, but cyclopentane, isopentane, n-pentane, isobutene,n-butaine, water (with bubbles of carbon dioxide), azo compound andargon are preferred because of their ozone layer protection capabilitiesand earth warming prevention capabilities, and cycropentane isespecially recommended for its heat-insulating characteristic.

In the exemplary embodiment, vacuum heat-insulator 16 is disposed on aside of outer box 9 of heat insulating box 2, and foam resinheat-insulator 17 on a side of inner box 10 of the box. Foam resinheat-insulator 17 fills space 14 between outer box 9 and inner box 10 byfoaming after vacuum heat-insulator 16 is disposed on inside surface ofouter box 9, forming a heat-insulating wall. Otherwise, vacuumheat-insulator 16 and foam resin heat-insulator 17 can be foamed into apiece, and the piece can be placed in space 14 between outer box 9 andinner box 10 so as a side of vacuum heat-insulator 16 may be placedfacing outer box 9. By directing non-flammable vacuum heat-insulator 16toward outer box of refrigerator main body 1, non-flammability ofrefrigerator main body 1 is further enhanced against an outside fire andthe safety of the refrigerator is augmented.

It is also possible to increase non-flammability of entireheat-insulating box 2 by placing multiple pieces of non-flammable vacuumheat-insulator 16 composed of board-shape molded inorganic fiber 18 on arear side, both sides and a top side of refrigerator main body 1,therewith the safety of the refrigerator is further augmented. Byplacing the vacuum heat-insulator on one or more places of heatinsulating box 2 corresponding to sides, a rear side and a bottom sideof freezing compartment 12, the heat-insulator is cost effectivelyplaced and heat-insulating performance is made more effective.

In the exemplary embodiment, door 4 attached to refrigerator main body 1employs board-shape molded inorganic fiber 18. As one way of usingvacuum heat-insulator 16 in door 4, vacuum insulator 16 composed ofboard-shape molded inorganic fiber 18 can be affixed to one of insidesfaces of door 4 facing inward or outward, and then foam resinheat-insulator 17 can fill rest of the inside space. In another way, amultilayer heat-insulating panel can be produced with vacuumheat-insulator 16 and foam resin heat-insulator 17, and then the panelcan be held inside door 4 or taped inside. Still in other way,board-shape molded inorganic fiber 18 can be directly disposed insidedoor 4, and then inside door 4 is evacuated, door 4 itself becomes avacuum heat-insulator. In any case, because non-flammable vacuumheat-insulator 16 or an equivalent is used in door 4, non-flammabilityof door 4 is achieved preventing refrigerator main body 1 from catchinga fire broken near the refrigerator.

The refrigerator in the exemplary embodiment has partition box 3dividing refrigerator main body 1 into independent compartments.Partition box 3 includes vacuum heat-insulator 16. The partition box canbe produced just by placing vacuum heat-insulator 16 inside partitionbox 3 and covering the box with partition box external frame 20 composedof ABS resin or of PP resin.

The partition box can be as well made by molding altogether the vacuumheat-insulator, the foam resin heat-insulator, and the partition boxexternal frame, or the partition box external frame and the inner boxcan be molded into a piece making the partition box. The partition boxcan also be made by producing a heat-insulating board with the vacuumheat-insulator and the foam resin heat insulator first, and then placingthe board in the external frame of the pattern box. In any case, as longas the vacuum heat-insulator is made of the board-shape inorganic fiber,other details are not specified. By constituting the partition box asabove and disposing the vacuum heat-insulator made of the board-shapeinorganic fiber inside the heat-insulating box, even if a fire is brokenoutside the refrigerator and a front door is opened burning inside, thefire is stopped moving to another compartment because the compartment isdetached by the partition box. As above, the refrigerator is insured ofa higher safety.

Partition box 3 separates inside refrigerator main body 1 intorefrigerating compartment 11 and freezing compartment 12, but theirpositional relationship is not specified; for instance, the freezer canbe one of a top freezer, a middle freezer and a bottom freezer. If therefrigerator is large, a vertical partition box can be installedseparating the room into right and left making either one a refrigeratoror a freezer.

In the exemplary embodiment, vacuum heat insulator is disposed in afollowing way. First, a hot-melt is applied to a side of vacuuminsulator 16, and the inside of the outer box where vacuumheat-insulator 16 is affixed, or to both places, and then vacuuminsulator 16 is press-fixed to heat insulating box 2. Next, foam resinheat-insulator 17 composed of the hard urethane foam is put into space14 between outer box 9 and inner box 10, foam-filling the space.

When vacuum heat-insulator 16 is affixed to the side part of heatinsulating box 2, vacuum heat-insulator 16 is disposed so as to fit intoa shape of heat insulating box 2. For instance, vacuum heat-insulator 16having a notch at right bottom corner as in FIG. 1 is disposed so as tofit into a shape of machinery compartment 21. At this time, the vacuumheat-insulator can cover an entire side part of the heat insulating box,or can cover only part of the insulating box corresponding to freezingcompartment 12 which leaks a large amount of heat, or the side part ofthe heat insulating box can be covered by a plurality of the vacuumheat-insulators.

Vacuum heat-insulator 16, which is placed on the heat-insulating part ofheat insulating box 2 detaching machinery compartment 21 in a rearbottom of refrigerator main body 1 from freezing compartment 12, is bentalong a shape of machinery compartment 21. Because vacuum heat-insulator16 is made of molded inorganic fiber 18 as the core material, bendingwork is easy and productivity is improved.

A fabrication method of vacuum heat-insulator 16 shown in FIG. 2 isdescribed below. After board-shape molded inorganic fiber 18 in athickness of 5 mm is dried at 140° C. for 1 hour, the dried material isplaced in cover material 19, and then inside of which is evacuated andopenings are sealed, providing vacuum heat-insulator 16. Chemicalingredients of the inorganic fiber in the board-shape molded inorganicfiber are approximately 60% of silica, approximately 18% of alumina,approximately 17% of calcium oxide, and approximately 5% of otherinorganic substance. Diameter of the fiber is 1 to 3 μm approximately.Approximately 5% of acryl binder is added to the compound as a binder.Density of the molded material is 120 kg/m³ in atmospheric pressure.

One side of cover material 19 is made up by a surface protect layer ofpolyethylene terephthalate (12 μm), an intermediate part of aluminumfoil (6 μm), and a heat seal layer of a laminate film of high-densitypolyethylene (50 μm). Another side a surface protect layer is made of asurface protect layer of polyethylene terephthalate (12 μm), anintermediate part of an aluminum vaporized film of ethylene-vinylalcohol copolymer resin (15 μm), and a heat seal layer a laminate filmof high-density polyethylene (50 μm).

In order to increase a protection capacity of cover material 19 fromdamage, a nylon resin layer is deposited on the surface-protect layer.Cover material 19 is in a shape of four-way seal bag.

Second Exemplary Embodiment

FIG. 3 is a cross-sectional view of a refrigerator in accordance with asecond exemplary embodiment of the present invention. Refrigerator mainbody 1 comprises heat insulating box 24 composed of outer box 22, innerbox 23, and board-shape molded inorganic fibers 18 disposed between theouter box and inner box. Heat insulating box 24 includes at least twosheets of board-shape molded inorganic fibers 18. Outer box 22 and innerbox 23 are made of a steel plate in a thickness of 0.5 mm, and jointsare weld-sealed keeping inside airtight. Partition box 25 is also madeof a steel plate, and board-shape molded inorganic fiber 18 is disposedin partition box 25. Outer box 22 and partition box 25 have exhaustvents 26 and 27 for vacuuming inside. After heat insulating box 24 andpartition box 25 are vacuumed, exhaust vents 26 and 27 are weld-shieldedfor keeping inside airtight. When welded, a protrusion of exhaust vent26 can be cut off for keeping a flatness of a rear plane of therefrigerator as long as the inside is kept airtight. Door 28 isstructured by an external frame made of a steel plate in a thickness of0.5 mm. After board-shape molded inorganic fiber 18 is disposed insidethe external frame, inside the door is evacuated and exhaust vent 29 issealed by welding.

Evaporator 8 is installed inside refrigerator main body 1 and connectedto components of external refrigeration cycle through pipes. The pipesand heat insulating box 24 are welded at joint 30 of inner box 23 andjoint 31 of outer box 23, keeping heat insulating box 24 airtight.

Board-shape molded inorganic fiber 18 has a depression made along thepipes where they are laid. Because the inorganic fiber is in a boardshape, forming the board is very easy and the depression can be formedeasily. The inorganic fiber contains approximately 18% of alumina. Thehigher the aluminum content in the organic fiber, the higher becomescrystallization ratio of the fiber therefore the higher becomesheat-resistant temperature of the fiber. By using board-shape moldedinorganic fiber 18 made of an inorganic fiber having a higher percentageof aluminum, the refrigerator is accordingly assured. of an enhancedsafety. It is also possible to include a gas absorbent in insulating box24 and door 28 for keeping inside airtight.

With the structure described above, because the insulating wall does notinclude foam resin insulator, safety of the refrigerator is greatlyenhanced. Even if the refrigerator is caught by an outside fire, theheat insulator does not burn because it does not include an organicinsulating material and because organic gas generation from the fiber isprevented with it. The outer box and the inner box are recommended to beproduced with a material having a high gas-barring characteristic and alow heat-conductivity, but a metal plate such as a very thin steel plateand a stainless plate are practically and effectively used.

Because the molded board-shape inorganic fiber is disposed between theouter box and the inner box, flatness of the heat insulating box ismaintained. Flatness of the surface of the refrigerator is therebymaintained even after the space between outer box and inner box isevacuated. In addition to it, because only the board-shape moldedinorganic fiber is placed in-between the inner box and the outer box andthe inside space is evacuated, productivity and work efficiency areenhanced higher than when an inorganic powder is used. Still more,because an inorganic fiber is used, gas generation from the vacuumheat-insulator over time is controlled to be small, and long termreliability of the heat insulating box is provided.

Composing the board-shape molded inorganic fiber includes at leastsilica, therewith heat-resistance of the board-shape molded inorganicfiber can be increased and a low cost of the product is achieved.

The larger the aluminum content is, the higher becomes theheat-resistance of the heat-insulating material. Therefore, by adding atleast aluminum to the board-shape molded inorganic fiber,non-flammability of the board-shape molded inorganic fiber is enhanced.The board-shape molded inorganic fiber can contain other non-organicingredients such as calcium oxide, magnesium oxide, iron oxide, titaniumoxide, boron oxide, sodium oxide, zirconia, calcium sulfide, magnesiumsulfide, silicon carbide, potassium titanate, chromium oxide and zincoxide, although the material is not limited to them.

The refrigerator in the exemplary embodiment employs HC refrigerant, arefrigerant less affecting global warming. When this kind of flammablerefrigerant is used, countermeasures against a fire become moreimportant than when conventional HCFC refrigerant or FC refrigerant areused. By using the heat-insulator made of an inorganic molded fiber asis demonstrated in the exemplary embodiment, a refrigerator having ahigh degree of safety can be provided. Namely, a refrigerator satisfyingboth requisitions for safety and earth environmental protection areprovided.

INDUSTRIAL APPLICABILITY

As described, a heat-insulating box of the refrigerator in accordancewith the exemplary embodiment of the present invention includes a vacuumheat-insulator composed of a board-shaped molded inorganic fiber coveredby a gas-barring film and decompressed inside. With this construction,non-flammability of the heat-insulator is enhanced higher than aheat-insulator employing foam resin and non-flammability of theheat-insulating box is enhanced. Because the non-flammability of theheat-insulating box against an outside fire is achieved, a much saferrefrigerator than a conventional refrigerator is provided.

1. A refrigerator comprising: a refrigeration cycle composed of acompressor, a condenser, a capillary tube and an evaporator linkedtogether forming a cycle; a heat insulating box including aheat-insulator, the heat-insulator is disposed in a space between aninner box facing inward of the refrigerator and an outer box facingoutward of the refrigerator, in which the space is sealed anddecompressed; and a board-shape molded inorganic fiber disposed in thespace as a heat insulator; and a flammable refrigerant enclosed in therefrigeration cycle.
 2. The refrigerator according to claim 1, whereinthe board-shape molded inorganic fiber includes at least silica.
 3. Therefrigerator according to claim 1, wherein the board-shape moldedinorganic fiber includes at least alumina.
 4. The refrigerator accordingto claim 1, wherein the heat insulating box does not include a foamresin insulator.
 5. The refrigerator according to claim 4, wherein thedensity of the board-shape molded inorganic fiber is at least 80 kg/m³and at most 400 kg/m³.
 6. The refrigerator according to claim 4, whereinthe density of the board-shape molded inorganic fiber is at least 150kg/m³ and at most 300 kg/m³.
 7. The refrigerator according to claim 4,wherein the heat insulating box additionally includes a gas absorbent.8. The refrigerator according to claim 4, wherein the board-shape moldedinorganic fiber is not placed in a gas-barring film.
 9. The refrigeratoraccording to claim 1, wherein the board-shape molded inorganic fiber isnot placed in a gas-barring film.
 10. The refrigerator according toclaim 1, wherein the heat insulating box does not include an organicinsulating material.